EPA/ROD/R09-92/084
1992
EPA Superfund
Record of Decision:
SACRAMENTO ARMY DEPOT
EPA ID: CA0210020780
OU04
SACRAMENTO, CA
09/30/1992
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SUPERFUND RECORD OF DECISION:
SACRAMENTO ARMY DEPOT
OXIDATION LAGOONS
OPERABLE UNIT
SACRAMENTO, CALIFORNIA
September 15, 1992
RECORD OF DECISION
I. DECLARATION
SITE NAME AND LOCATION
Oxidation Lagoons Operable Unit
Sacramento Army Depot (SAAD)
8350 Fruitridge Road
Sacramento, California
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action for the Oxidation Lagoons Operable
Unit at the SAAD facility in Sacramento, California, which was chosen in accordance with The
Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) , as
amended by The Superfund Amendments and Reauthorization Act of 1986 (SARA) , and, to the extent
practicable, the National Oil and Hazardous Substances Pollution Contingency Plan (NCP). The
basis for this decision is documented in the administrative record for this site, which
includes, among other documents:
• The Oxidation Lagoons Operable Unit Feasibility Study (OUFS) which contains site
investigation data, the Public Health Evaluation, and an analysis of remedial
alternatives,
• The Proposed Plan (PP), dated April 1992, which summarizes the preferred cleanup
alternative, compares the preferred alternative with several other alternatives, and
invites public participation,
• Summaries of public comments on the OUFS and the PP, including the Army's response
to comments.
The purpose of this Record of Decision (ROD) is to set forth the remedial action to be conducted
at SAAD to remedy soil contamination associated with the Oxidation Lagoons. This is the third
of several potential remedial actions addressing soil and groundwater contamination that may be
conducted at SAAD. Subseguent RODs will address other potential threats posed by the site, both
on and off site. A final comprehensive ROD will address the entire SAAD facility prior to
SAAD's closure in 1997.
The U.S. Environmental Protection Agency Region IX (EPA IX) and the State of California
[California EPA: Department of Toxic Substances Control (DTSC) and Central Valley Regional
Water Quality Control Board (CVRWQCB)] concur with the selected remedy.
ASSESSMENT OF THE SITE
The Oxidation Lagoons Operable Unit includes four Oxidation Lagoons, the Drainage Ditches, and a
portion of Old Morrison Creek. An investigation by the U.S. Army showed that soils in the
Oxidation Lagoons Operable Unit have been contaminated by metals. Metals identified at
concentrations above background levels are antimony, arsenic, cadmium, chromium, cobalt, copper,
lead, mercury, nickel, silver, and zinc.
Contamination in the lagoons appears to extend laterally to the intermediate level of the berms
which surround each lagoon. The lateral extent of contamination in the Drainage Ditches is
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approximately 6 feet wide, and the total length of the ditches. The lateral extent of
contamination in Old Morrison Creek is about 30 feet wide, and extends from approximately 50
feet east of the eastern Drainage Ditch to Caroline Drive. The vertical extent of contamination
is about 2 feet in the lagoons, and about 3 feet in the ditches and the creek.
The Oxidation Lagoons Operable Unit does not include groundwater. Comparison of soil
contaminants with the types of contaminants present in groundwater indicates that the Oxidation
Lagoons Unit is not currently a source of groundwater contamination found at SAAD.
A baseline health risk assessment was conducted to evaluate the current and potential future
risks posed by the contamination at the Oxidation Lagoons Operable Unit if no cleanup occurs.
The health risk assessment found that arsenic, cadmium and lead pose the greatest potential
threat to human health, due to their toxicity and concentrations. Cleanup levels based on
potential health risks and on protection of groundwater were then established for arsenic,
cadmium and lead. The cleanup levels were determined based on additive risk and Applicable or
Relevant and Appropriate Reguirements.
Actual or threatened released of hazardous substances from this site, if not addressed by
implementing the response action presented in this ROD, may present an imminent and substantial
endangerment to public health, welfare, or the environment.
DESCRIPTION OF THE SEIiECTED REMEDY
The Army intends to clean up the Oxidation Lagoons Operable Unit so that the public is not
exposed to toxic chemicals from the site. This ROD addresses the principal threat at the
Oxidation Lagoons site by removing the contaminants present in the soil. Removal of
contaminants in the soil will reduce the potential for: future migration of contamination from
the soil to groundwater; public exposure to contamination from inhalation or ingestion of
fugitive dust containing contaminants; and public exposure to contamination due to direct
contact or ingestion of contaminated soil. These pathways represent the primary potential
present and future risks to public health. Inhalation or ingestion of fugitive dust by the
nearest off-site business and residence is presently a potential risk. Exposure to
contamination due to groundwater ingestion, or direct contact or ingestion of contaminated soil
are potential future risks.
The selected remedy for cleaning up the soil at the Oxidation Lagoons Operable Unit is composed
of: excavating contaminated soil; treating soil in an on-site washing unit; backfilling the
excavation with remediated soil; treating the soil-wash rinsate on site to precipitate metals;
and reclamation of metals from the de-watered sludge or off-site disposal of the sludge. The
selected remedy includes:
• Excavating soil that contains levels of arsenic, cadmium, and/or lead above cleanup
levels.
• Removing metals from the soil by mixing it with a washing reagent for a selected
reaction time.
• Sampling the washed soil to assess the effectiveness of the cleanup. Remediated soil
then will be used to backfill the excavation.
• Treating the soil-wash rinsate on site using a chemical precipitant.
• De-watering the sludge containing the precipitated metals on site, and disposing of
it at an off-site facility permitted to receive hazardous waste or recovering the
precipitated metals at an offsite metal reclamation unit. Although reclamation of
the sludge is preferred to off-site disposal, the decision will be based on the
cost, the concentration of metals in the sludge, the total guantity of sludge, and
the availability of a market for metals recycling.
• Sampling the treated rinsate to assess its guality. Treated rinsate will be
discharged to the sanitary sewer.
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• Completing the excavation and treatment within six to nine months after contractor
selection.
STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the environment, complies with Federal and
State requirements that are legally applicable or relevant and appropriate to the remedial
action, and is cost-effective. This remedy utilizes permanent solutions and alternative
treatment technologies, to the maximum extent practicable, and satisfies the statutory
preference for remedies that employ treatment that reduces toxicity, mobility, or volume as a
principal element. Because the remedial action will not leave hazardous residuals on site above
health-based levels and will be completed after approximately six to nine months of operation,
the five-year review will not apply to this action.
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RECORD OF DECISION
II. DECISION SUMMARY
SAAD - OXIDATION LAGOONS OPERABLE UNIT
TABLE OF CONTENTS
Chapter
1 SITE NAME, LOCATION, AND DESCRIPTION
1.1 Location
1.2 Site Description
1.3 Demography
1.4 Land Use
1.5 Climatology
1.6 Regional Topography
1.7 Surface Water Hydrology
1.8 Geology
1.9 Hydrogeology
1.10 Natural Resources
2 SITE HISTORY AND ENFORCEMENT ACTIVITIES
3 HIGHLIGHTS OF COMMUNITY INVOLVEMENT
4 SCOPE AND ROLE OF OPERABLE UNIT WITHIN SITE STRATEGY
5 SUMMARY OF SITE CHARACTERISTICS
5.1 Contamination Sources
5.2 Evaluation of Primary Contaminants
5.3 Location of Contaminants and Potential Routes of Migration
6 SUMMARY OF SITE RISKS
6.1 Human Health Risks
6.1.1 Contaminants of Concern
6.1.2 Exposure Assessment
6.1.3 Summary of PHE Results
6.2 Environmental Evaluation
6.3 Cleanup Levels
6.3.1 Non-Carcinogens
6.3.2 Carcinogens
7 DESCRIPTION OF ALTERNATIVES
7.1 Alternative 1: No Action
7.2 Alternative 2: Excavation, On-Site Soil Washing, On-Site Treatment of Wash Liguid, and
Backfill
7.3 Alternative 3: Excavation, On-Site Soil Washing, Off-Site Disposal of Wash Liguid, and
Backfill
7.4 Alternative 4: Excavation, Stabilization, and Backfill with Stabilized Soil
7.5 Alternative 5: Excavation, Stabilization, Backfill with Stabilized Soil, and Cap
8 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
8.1 Criterion 1: Overall Protection of Human Health and the Environment
8.2 Criterion 2: Compliance with ARARs
8.3 Criterion 3: Long-Term Effectiveness and Permanence
8.4 Criterion 4: Reduction of Toxicity, Mobility, and Volume Through Treatment
8.5 Criterion 5: Short-Term Effectiveness
8.6 Criterion 6: Implementability
8.7 Criterion 7: Cost
8.8 Criterion 8: State Acceptance
8.9 Criterion 9: Community Acceptance
SELECTED REMEDY
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10 STATUTORY DETERMINATIONS
10.1 Protection of Human Health and Environment
10.2 Compliance with ARARs
10.3 Cost Effectiveness
10.4 Utilization of Permanent Solutions, and Alternative Treatment and Resource Recovery
Technologies
10.5 Preference for Treatment as a Principle Element
11 DOCUMENTATION OF SIGNIFICANT CHANGES
12 REFERENCES CITED
FIGURES
1 Site Location Map - Sacramento Army Depot
2 Site Location Map - Oxidation Lagoons Operable Unit
3 Horizontal Extent of Contamination
4 Vertical Extent of Contamination, Cross Sections A-A and B-B
TABLES
1 Summary of Contaminants
2 Definitions of Risk Terms
3 Estimated Exposure Point Concentrations
4 Carcinogenic Risks
5 Non-Carcinogenic Risks
6 Contaminant Concentrations & Cleanup Levels in Soil
7 Selected Remedy Estimated Costs
RECORD OF DECISION
III. RESPONSIVENESS SUMMARY
SAAD - OXIDATION LAGOONS OPERABLE UNIT
APPENDICES
A Analysis of ARARs
B Administrative Record Documents
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1 SITE NAME, LOCATION, AND DESCRIPTION
1.1 Location
The Oxidation Lagoons Operable Unit is part of the Sacramento Army Depot (SAAD) military
facility owned by the U.S. Army. The SAAD facility is located at 8350 Fruitridge Road, in the
City and County of Sacramento, California. SAAD lies approximately 7 miles southeast of downtown
Sacramento (Figure 1), and is bound by Fruitridge Road on the north, Florin-Perkins Road on the
east, Elder Creek Road on the south, and the Southern Pacific Railroad tracks on the west. The
facility encompasses an area of 485 acres.
The four Oxidation Lagoons, each covering approximately 0.5 to 0.75 acres, are located in the
southwest guadrant of the SAAD facility, north of the Burn Pits and east of Caroline Drive.
North of the lagoons are the Drainage Ditches and Old Morrison Creek. The Operable Unit
includes the four lagoons, the Drainages Ditches, and a portion of Old Morrison Creek. A site
map of the SAAD facility, showing the location of the Oxidation Lagoons Operable Unit with
respect to the other Operable Units and site features, is shown on Figure 2.
1.2 Site Description
Past and present activities conducted at SAAD include electro-optics eguipment repair, the
emergency manufacture of parts, shelter repair, metal plating and treatment, and painting. The
metal plating and painting operations are likely the primary on-site waste generating
activities.
In addition to the Oxidation Lagoons, past and present surface and subsurface storage units and
other structures at the site include: several underground and above-ground storage tanks;
unlined burn pits; a battery disposal area; areas where pesticides were mixed or pesticide rinse
water may have been discharged to the ground surface; and an area used for firefighter training,
where flammable hydrocarbons were reportedly burned on the ground surface. Several of these
areas have released contaminants into the soil and/or groundwater at SAAD, and are being
investigated and cleaned up as separate Operable Units. Areas where contaminants have been found
at SAAD are discussed in more detail in Section 2.
1.3 Demography
In 1987, 76 people were living on the SAAD facility, and 56,398 people were living off site,
within 2 to 3 miles of SAAD. Data for the working populations on and around SAAD in 1987 are
not available. In 1984, 3,430 people worked on the SAAD facility and 20,710 worked off site,
within 2 to 3 miles of SAAD.
1.4 Land Use
SAAD is surrounded on all sides by land currently zoned as commercial/light industrial property.
Within 2 to 3 miles of SAAD, the areas that are primarily low to medium density residential are
northwest, west, and southwest of the site. The areas south, east, and north of SAAD are
primarily industrial.
1.5 Climatology
Climate at SAAD is classified as "Mediterranean", hot summer (Koppen System), with mean
temperatures of 30 to 40 degrees Fahrenheit in January, and 90 to 100 degrees in July. Average
relative humidity in January ranges from 80 to 90 percent, and from 50 to 60 percent in July.
Generally, 85 to 95 percent of the annual precipitation occurs in winter. The estimated mean
annual precipitation at the site is 17 inches, and the estimated mean evaporation is 73 inches.
1.6 Regional Topography
SAAD is located in the Central Valley of California, a broad, flat valley that lies between the
Sierra Nevada to the east and the Coast Ranges to the west. The youngest sediments (as old as 5
million years) underlying SAAD were deposited by the American River as its course meandered
across the valley floor, and, to a lesser extent, by Morrison Creek. Conseguently, the
topography at SAAD is relatively flat. The slope of the land surface is approximately 0.13
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percent to the west, with ground surface elevations ranging from 36 to 42 feet above mean sea
level.
1.7 Surface Water Hydrology
SAAD is situated within the Morrison Creek drainage basin. Morrison Creek originally flowed from
east to west through the land now occupied by the SAAD facility. When SAAD was constructed, the
Army re-routed Morrison Creek so that it flowed along the facility boundary around the south
side of the facility, rather than through it. The floodplain for the re-routed Morrison Creek
extended approximately half a mile north of the creek, onto the SAAD facility. The creek
discharges into two overflow basins of the Sacramento and American Rivers, and ultimately
empties into the Sacramento River.
In 1958, 7,900 linear feet of flood-control dikes were constructed along the re-routed portion
of Morrison Creek, and in 1986, the new channel was widened and deepened. The re-routed portion
of Morrison Creek is currently capable of handling 100-year flood events, so SAAD is not
considered to be on the floodplain at this time. The old channel of Morrison Creek is currently
dry during most of the year. This channel bisects the facility from east to west and is
referred to as "Old Morrison Creek".
Drainage of the SAAD facility is mainly overland flow to Morrison Creek and man-made diversion
structures. Morrison Creek also receives surface runoff from other industrial and agricultural
sites which are located along its course, and permitted discharges from industries.
A study of the SAAD facility indicates that 0.52 acres of wetlands currently exist within the
Oxidation Lagoons Operable Unit, along Old Morrison Creek.
1.8 Geology
SAAD is located in the Great Valley of California, a broad asymmetric trough filled with a thick
assemblage of flat-lying marine and non-marine sediments. The most recent formations deposited
in the Great Valley are nonmarine sediments derived from the Sierra Nevada foothills and
mountains on the west side of the valley and from the Coast Ranges on the east side of the
valley. The sediments are carried out of the mountains and deposited by a series of large and
small rivers. Sediments under SAAD have been largely derived from the Sierra Nevadas, and have
been deposited by the American River as it has meandered back and forth across the valley floor.
The upper 250 feet of sediments under SAAD is comprised of interbedded sands, silts and clays,
with some coarse gravels underlying the north side of the facility at an approximate depth of 40
feet. The identification of horizontal and vertical boundaries of formation is extremely
difficult in alluvial environments such as that encountered at SAAD. Older buried stream
channels exist at various locations and depths in the area. These streams have deposited
materials ranging in size from gravel down to clay as they meandered back and forth. Multiple
discontinuous hardpans (cemented clays), representing buried ancient soil horizons, exist
throughout the site.
1.9 Hydrogeology
SAAD is underlain by a series of alluvial aguifers which provide water to residences,
industries, and agricultural properties in Sacramento County. The California Department of Water
Resources has divided the groundwater in the area into two hydraulically isolated sections, the
superjacent (upper) series located form approximately 80 to 250 feet in depth under the site and
the subjacent (lower) series located deeper than approximately 250 feet under the site. The
primary water-producing aguifers are in the subjacent series, although many wells in the
surrounding area draw water from the superjacent series. Groundwater contamination under the
SAAD facility has been found in three discrete, relatively thin, strata located within the upper
portion of the superjacent series, approximately 80 to 200 feet below ground surface.
Groundwater contamination extends off site to the southwest of the SAAD facility. The lateral
extent of groundwater contamination is currently being investigated, but appears to extend
approximately 1,000 feet southwest of SAAD. Industries and residences in this area use City
water from municipal wells located at least 3/4 mile from SAAD.
1.10 Natural Resources
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Except for groundwater, which is an extremely important resource throughout the Central Valley,
other natural resources on the site are minimal. The Army Corps of Engineers does not consider
the wetlands at SAAD to be high guality wetlands because they provide minimal wetland functions
and habitat values. The Army plans to restore the wetlands areas following remediation by
restoring the relict channel of Morrison Creek to its original grade and by revegetating the
impacted wetland areas with seed source material from areas of old Morrison Creek that are
currently jurisdictional wetlands. It is expected that there will be an overall benefit to
environmental guality by eliminating a source of contamination to species in the area.
2 SITE HISTORY AND ENFORCEMENT ACTIVITIES
The Remedial Investigations conducted at SAAD are a part of the U.S. Army Installation
Restoration Program (IRP). The Army is the owner of the site and the lead agency for
implementing the environmental response actions.
In the late 1970s, the U.S. Army Depot Systems Command recommended that SAAD be included in the
Installation Restoration Program (IRP). Conseguently, in 1978 and 1979 the U.S. Army Toxic and
Hazardous Materials Agency (USATHMA) conducted a review of historical data to assess SAAD with
regard to the use, storage, treatment, and disposal of toxic and hazardous materials. USATHMA
identified several areas of concern where further investigation was warranted.
In early 1981, the Army initiated an on-site investigation of soil and groundwater in the areas
of concern identified by USATHMA, including the Oxidation Lagoons, Burn Pits, Pesticide Mix
Area, Morrison Creek, and Old Morrison Creek. Groundwater samples collected during this
investigation indicated that volatile organic chemicals (VOCs) were present in groundwater under
the southwest corner of SAAD. Based on the location of the VOCs in groundwater, the Burn Pits
appeared to be one of the main sources of groundwater contamination in this area. The Oxidation
Lagoons were identified as an area contaminated with metals.
In late 1981, the Central Valley Regional Water Quality Control Board (CVRWQCB) sampled off-site
wells near the southwest corner of SAAD. VOCs were reported in some of the wells closest to
SAAD, and the Army began working with the CVRWQCB to assess the source and extent of groundwater
contamination. The U.S. EPA and California Department of Health Services (DHS) subseguently
becameinvolved in the investigation of contamination at SAAD, and SAAD was placed on the
National Priorities List (NPL), effective August 21, 1987 (52 Fed. Reg. 27620; July 22, 1987).
In December 1988, the U.S. Army, the U.S. EPA, and the State of California signed a Federal
Facility Agreement (FFA) under CERCLA Section 120 agreeing to address the entire facility,
including the contaminated groundwater and seven other areas of suspected contamination on the
SAAD facility:
Tank 2
• Oxidation Lagoons
• Burn Pits
Building 320 Leach Field
• Pesticide Mix Area
• Firefighter Training Area
• Battery Disposal Well
The FFA also calls for a rigorous RCRA Facility Assessment to identify other specific Solid
Waste Management Units that need further characterization and cleanup. To expedite
investigation and cleanup of the individual sites, the seven areas listed above and the on-site
groundwater are each being treated as individual Operable Units. These seven Operable Units are
shown on Figure 2. Groundwater was the first Operable Unit investigated, and is currently being
cleaned up under a ROD signed in 1989. Contaminated soil at the Tank 2 Operable Unit is
scheduled to be cleaned up next, under the provisions of a ROD that was signed in December 1991.
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Built in 1950, the Oxidation Lagoons received most of the industrial and domestic wastewater
generated at SAAD until 1972. Domestic wastewater was treated in the sewage treatment plant
prior to discharge to the lagoons. Concentrated, untreated rinse water generated by metal
plating operations was diluted with large volumes of water and then directed to the lagoons.
Until 1968, this water was supplied by two on-site wells. In 1968, the wells were abandoned and
SAAD was connected to the City of Sacramento municipal water supply.
Currently, the four Oxidation Lagoons are not in use, and are dry. Vegetation is present in
three of the lagoons. The bottom of the southwest Oxidation Lagoon is void of vegetation,
apparently due to hardpan soil exposed at the surface.
As part of the IRP, the U.S. Army conducted additional soil assessments at the Oxidation Lagoons
in 1985, 1986 and 1990 through 1991. In 1991, the U.S. Army prepared a Remedial Investigation/
Feasibility Study (RI/FS) workplan in accordance with the FFA. The RI/FS evaluated the seven
Operable Units. Based upon the RI/FS findings, four of these, including the Oxidation Lagoons,
were recommended for operable unit feasibility studies (OUFS).
The Oxidation Lagoons were recommended for an OUFS because: 1) heavy metals are present in the
near surface, and pose a threat for airborne migration or migration in surface water runoff; and
2) the Toxic Pits Cleanup Act (TPCA) is an Applicable or Relevant and Appropriate Requirement
(ARAR). TPCA requires that surface impoundments be closed as soon as feasible.
An OUFS for the Oxidation Lagoons was prepared in 1991, and was revised March 13, 1992. As part
of the OUFS, the Army prepared a baseline Public Health Evaluation (PHE) to estimate potential
health and environmental risks that could results if no action was taken at the site. The PHE
indicated potential cancer and non-cancer health effects to an on-site resident from metals in
Oxidation Lagoons soils. Details of the PHE are summarized in Section 6.
3 HIGHLIGHTS OF COMMUNITY INVOLVEMENT
In June 1988, the Army prepared a Community Relations Plan. In August, 1991, the U.S. Army
issued a Proposed Plan (PP) for the Oxidation Lagoons Operable Unit. The plan consists of a
10-page fact sheet that was mailed to residents in the surrounding community. The plan describes
the site background, presents a summary of site contamination, and discusses health risks,
cleanup levels, and remedial alternatives. The plan also includes a list of individuals who may
be contacted for additional information, lists the addresses of the information repositories,
and announces the public comment period. The Army also placed notices in two local daily
newspapers, the Sacramento Bee and the Sacramento Union, for five days prior to the public
comment period to outline the preferred remedial alternative and to announce the availability of
the OUFS and PP, as part of the Administrative Record, for review and comment. The SAAD
Administrative Record was located at the following local repositories: SAAD Visitor Control
Center and the California State University, Sacramento, Library. The OUFS and PP were also
available for public review at the Sacramento office of the Department of Toxic Substances
Control (DTSC) and at EPA headquarters in San Francisco.
A public comment period was held from August 20 through September 18, 1991. A public meeting was
held on August 20, 1991. Thirty-nine people, including community members and representatives
from the Army, U.S. EPA, DTSC, and CVRWQCB attended the public meeting. Seven oral questions
were received at the meeting. In April 1992, the U.S. Army revised and reissued the PP for the
Oxidation Lagoons Operable Unit in order to include additional information on compliance with
Land Disposal Regulations that are applicable to the site. A second public comment period was
held from May 9 through June 8, 1992. A second public meeting was held on May 27, 1992. No
written comments were received during either public comment period.
Details of community involvement activities and responses to official public comments on the PP
are presented in the Responsiveness Summary, which is in Part III of this ROD.
In addition, the DTSC adopted a Negative Declaration fulfilling the requirements found under the
California Environmental Quality Act.
4 SCOPE AND ROLE OF OPERABLE UNIT WITHIN SITE STRATEGY
Since the Army began investigating possible contamination at SAAD, eight Operable Units have
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been identified that may require remediation (see Section 2, above). Four of the units, the
Oxidation Lagoons, Tank 2, the Burn Pits, and On-site Groundwater, were recommended for OUFS.
The other four units will be addressed in the overall site Feasibility Study as the important
site characterization information becomes available.
The Groundwater OUFS was completed on May 19, 1989, and on-site groundwater is currently being
remediated under a ROD signed on September 29, 1989. The OUFS for Tank 2 was finalized on
October 1, 1991. A ROD for Tank 2 was signed in December 1991, and remedial activities at Tank
2 are scheduled to begin in 1992. The OUFS for the Oxidation Lagoons was finalized on March 13,
1992. The OUFS for the Burn Pits is scheduled to be completed in 1992. Subsequent RODs will
address other potential threats posed by the site. Also, there will be a final ROD that will
comprehensively address all of the contaminated areas at SAAD.
The remedy selected in this ROD will address metals contamination in soils at the Oxidation
Lagoons operable unit. These metals pose the principle risk through ingestion of, or contact
with, the contaminated soil.
5 SUMMARY OF SITE CHARACTERISTICS
5.1 Contamination Sources
Soil from the ground surface to depths of approximately 18 to 36 inches beneath the Oxidation
Lagoons Operable Unit (consisting of the four lagoons, the Drainage Ditches, and Old Morrison
Creek) contain 11 heavy metals at concentrations that exceed site background concentrations.
The source of these metals appears to be waste water that was discharged to the Oxidation
Lagoons and, subsequently, to the three Drainage Ditches and Old Morrison Creek. Most of the
waste water appears to have been generated by electroplating operations at the Depot. These
electroplating wastes are listed as F006 wastes under the Resource Conservation and Recovery Act
(RCRA) (40 CFR 261.31).
5.2 Evaluation of Primary Contaminants
Soil sample analytical results indicate that heavy metals are present in surficial soils of the
Oxidation Lagoons. Seventeen metals were detected in at least one sample of the Oxidation
Lagoons soils; each of these plus five additional metals were detected in at least one sample
from the Drainage Ditches and Old Morrison Creek. The estimated volume of affected soil at the
Oxidation Lagoons is approximately 12,000 in-place cubic yards (cy). The estimated volume of
affected soil at the Drainage Ditches and Old Morrison Creek is 3,500 in-place cy. The 22
metals detected are:
Many of these metals are naturally occurring in the soils at SAAD. Therefore, the area around
the Oxidation Lagoons Operable Unit was studied to establish the normal (background)
concentration of each metal. Eleven of the detected metals were identified above background
levels: antimony, arsenic, cadmium, chromium, cobalt, copper, lead, mercury, nickel, silver,
and zinc. A list of these metals, the percentage of times each was detected, the range of
concentrations reported by the analytical laboratory, the range of background concentrations,
the relative mobility of each metal, and its classification as a carcinogen or non-carcinogen,
are presented in Table 1.
5.3 Location of Contaminants and Potential Routes of Migration
The estimated lateral extent of contamination in the Oxidation Lagoons is shown in Figure 3.
The extent was estimated based upon the postulated maximum operating water levels in the
lagoons, as approximated from topographic surveys. Contamination appears to extend laterally to
the intermediate level of the berms which surround each lagoon. The lateral extent of
contamination in the Drainage Ditches is approximately 6 feet wide, and extends along the total
length of the ditches. The lateral extent of contamination in Old Morrison Creek is about 30
feet wide, and extends from approximately 50 feet east of the east Drainage Ditch to Caroline
Drive. Based upon soil sample analytical results, metals contamination in the lagoons is
concentrated in the upper 2 feet of soil (Figure 4). The vertical extent of contamination in
the Drainage Ditches and Old Morrison Creek is about 3 feet.
Since metals are present in surface soils, airborne migration could occur in windblown dust.
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Individuals on site could be exposed via inhalation of the dust, or by directly contacting
surface soil during outdoor activities. Individuals off site could be exposed to windblown dust.
Groundwater, which is at a depth of about 80 feet beneath the unit, has not been affected by
metals from the Oxidation Lagoons. In the future, the metals could dissolve in infiltrating
rainwater and migrate downward to the underlying groundwater, and a resident or business having
a well downgradient of the unit could be exposed. However, contaminants have only been detected
in the top 18 to 36 inches of soil, which suggests that the potential for mobility into
groundwater is low. A numerical mobility assessment was performed to estimate future movement
of metals at the site. This assessment indicated that the contaminants will move approximately 2
to 6 feet vertically downward over the next 100 years.
6 SUMMARY OF SITE RISKS
6.1 Human Health Risks
As part of the OUFS, the Army prepared a baseline PHE. This PHE was prepared to estimate, in
the absence of remedial action (i.e., the "No Action" alternative), the potential future risks
to human health by contaminants remaining in soil or leaching through soil, migrating in
groundwater, or released to the air. Table 2 presents definitions of key risk terms from the
PHE that are used in this section of the ROD.
6.1.1 Contaminants of Concern
The risk assessment provides a list of contaminants based on the results of the RI that were
found above detection limits or above natural background levels. Eleven metals of potential
concern were identified above background levels and appeared to originate from the Oxidation
Lagoons, Drainage Ditches, and Old Morrison Creek. The PHE estimated the risk posed by all 11
metals. The following three metals are the primary chemicals of concern based on the estimated
health risks and on the freguency of detection:
• Arsenic: Classified as a Group A carcinogen (known human carcinogen)
• Cadmium: Classified as a Group Bl carcinogen (probable human carcinogen, limited
human data)
• Lead: classified as a Group B2 carcinogen (probable human carcinogen, no human
data). The most notable effect of lead exposure is decreased neurological
development in children.
6.1.2 Exposure Assessment
Four exposure points were considered for the PHE:
• a hypothetical residence constructed on site at the Oxidation Lagoons following
closure of SAAD;
• a hypothetical residence constructed on site at the Drainage Ditches and Old
Morrison Creek following closure of SAAD;
• the nearest off-site business downgradient from the Oxidation Lagoons operable unit
which has a well; and
• the nearest off-site residence downgradient from the Oxidation Lagoons operable unit
which has a well.
The first two exposure scenarios were selected because SAAD is scheduled to close in the future
and the site could be re-zoned and used for residential development. Future residential
development is considered unlikely, but is a health-conservation assumption. The latter two
exposure points presently exist. The approximate locations of the current off-site receptors are
shown on Figure 2.
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TABIiE 2
DEFINITIONS OF RISK TERMS
Carcinogen: A substance that, with long term exposure, may increase the incidence of cancer.
Chronic Daily Intake (GDI): The average amount of chemical in contact with an individual on a
daily basis over a substantial portion of a lifetime.
Chronic Exposure: A persistent, recurring, or long-term exposure. Chronic exposure may result
in health effects (such as cancer) that are delayed in onset, occurring long after exposure
ceased.
Exposure: The opportunity to receive a dose through direct contact with a chemical or medium
containing a chemical.
Exposure Assessment: The process of describing, for a population at risk, the amounts of
chemicals to which individuals are exposed, or the distribution of exposures within a
population, or the average exposure of an entire population.
Health Hazard Index (HHI): An EPA method used to assess the potential noncarcinogenic risk.
The ratio of the GDI to the chronic RfD (or other suitable toxicity value for noncarcinogens) is
calculated. If it is less than one, then the exposure represented by the GDI is judged unlikely
to produce an adverse noncarcinogenic effect. A cumulative, endpoint-specific HHI can also be
calculated to evaluate the risks posed by exposure to more than one chemical by summing the
GDI/RfD ratios for all the chemicals of interest that exert a similar effect on a particular
organ. This approach assumes that multiple subthreshold exposures could result in an adverse
effect on a particular organ and that the magnitude of the adverse effect will be proportional
to the sum of the ratios of the subthreshold exposures. If the cumulative HHI is greater than
one, then there my be concern for public health risk.
Reference Dose (RfD): An estimate, with uncertainty spanning an order of magnitude, of a daily
exposure level for human population that is likely to be without an appreciable risk of
deleterious effects.
Risk: The nature and probability of occurrence of an unwanted, adverse effect on human life,
health, or on the environment.
Risk Assessment or Health Evaluation: The characterization of the potential adverse effect on
human life, health, or on the environment. According to the National Research Council's
Committee on the Institutional Means for Assessment of Health Risk, human health risk assessment
includes: (1) description on the potential adverse health effects based on an evaluation of
results of epidemiologic, clinical, toxicologic, and environmental research; (2) extrapolation
from those results to predict the types and estimate the extent of health effect in humans under
given conditions of exposure; (3) judgements as to the number and characteristics of persons
exposed at various intensities and durations; (4) summary judgements on the existence and
overall magnitude of the public-health program; and (5) characterization of the uncertainties
inherent in the process of inferring risk.
Slope Factor: A plausible upper-bound estimate (set at 95%) of the probability of a response
per unit intake of a chemical over a lifetime.
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Metals from the Oxidation Lagoons do not appear to have impacted groundwater guality to date.
For the PHE, however, the assumptions were made that: metals may migrate into the underlying
groundwater as components of leachate at some time in the future; metals present in surface
soils may enter the atmosphere in windblown dust; and individuals located on site may directly
contact soil. Thus, the following potential exposure pathways were considered: soil ingestion,
dermal absorption, drinking water ingestion, and inhalation of dust for on-site individuals; and
ingestion of drinking water and inhalation of dust for off-site individuals.
Metals detected in the top six inches of soil were assumed to pose a potential risk because the
concentrations are greatest near the soil surface. Analytical results for soil samples collected
within the four Oxidation Lagoons and along the Drainage Ditches and Old Morrison Creek were
used to calculate average and upper-bound concentrations for each of the metals found above
background concentrations. The calculated upperbound concentration for each metal is the 95%
Upper Confidence Limit concentration, calculated by finding the arithmetic mean and adding two
times the standard deviation. Upper-bound soil concentrations were used for calculating
exposure point concentrations for direct contact with contaminated soil, and inhalation of dust.
Estimated exposure point concentrations of the three primary metals of concern in soil and in
fugitive dust are shown on Table 3.
Upper-bound groundwater exposure point concentrations were estimated based upon soil
concentrations, physical and chemical properties of the metals, physical characteristics of the
uppermost water-bearing zone, and net precipitation infiltration at the site. Upper-bound metal
concentrations in the contaminated soil were input to a vadose zone model to derive upperbound
leachate concentrations. It was assumed that the source concentrations stayed constant
over time (i.e., leaching of metals does not deplete the source). The calculated leachate
concentrations were then used to estimate the on-site upper-bound groundwater concentrations
directly beneath the lagoons, the Drainage Ditches, and Old Morrison Creek. These groundwater
concentrations were assumed to remain constant over a 70-year exposure period. A groundwater
transport computer model was used to estimate upper-bound groundwater exposure concentrations
off site. Estimated upper-bound exposure point concentrations of the three primary metals of
concern in groundwater are shown on Table 3.
The contaminant intake eguations and values chosen for various intake parameters were derived
from the standard intake eguations and data presented in EPA guidance documents. Chronic Daily
Intake (GDI), the amount of each chemical that could be inhaled, ingested, or adsorbed, were
estimated in the PHE. The estimated GDIs are shown on Tables 4 and 5. The GDIs were then
multiplied by chemical-specific slope factors (SF) to calculate carcinogenic risk. The SF
represents the 95 percent upper confidence limit (UCL) value of the probability of a
carcinogenic response per unit intake of a contaminant over a lifetime (70 years for the
analysis in the PHE). SF values for arsenic and cadmium are presented in Table 4. No SF has
been established for lead. Therefore, lead is not included on Table 4.
To calculate the Health Hazard Index (HHI) for non-carcinogenic risks, the GDIs were multiplied
by chemical-specific Reference Dose (RfD) values. The RfD values for a substance represent a
level of intake which is unlikely to result in adverse non-carcinogenic health effects in
individuals exposed for an extended period of time (70 years for the analysis in the PHE). RfDs
for the arsenic and cadmium are shown on Table 5. U.S. EPA Health Criteria are not available
for lead at this time so lead is not included on Table 5.
6.1.3 Summary of PHE Results
The PHE estimated the potential non-carcinogenic and carcinogenic risks posed by each of the 11
metals of concern at the Oxidation Lagoons Operable Unit to Future On-site Residents, and to the
nearest Off-site Residence and Business. (Dose-response criteria are not available for two of
the metals, cobalt and lead. These metals were evaluated separately).
Carcinogenic risks were estimated for arsenic and cadmium by multiplying the GDI of each metal
by its SF. The carcinogenic risks for arsenic and cadmium, expressed as the "potential excess
cancer risk", for each exposure pathway are shown on Table 4. As a National goal, the EPA's
target risk range is 10 [-4] to 10[-6], or one additional incidence of cancer per 10,000 people
to one additional incidence of cancer per 1,000,000 people. The aggregate (total) estimated
carcinogenic risks from arsenic and cadmium due to the combined effects of all pathways are:
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• Approximately 2.4 excess cancers per 10,000 people for Hypothetical Future Oxidation
Lagoons Residents;
• Approximately one excess cancer per 10,000 people for Hypothetical Future Drainage
Ditches and Old Morrison Creek Residents;
• Less than one excess cancer per one million people for off-site businesses and
off-site residents.
Thus, the baseline risk estimated for Future Oxidation Lagoon Residents is higher than the
target range. The baseline risks for the other exposure scenarios are within or less than the
target range.
The non-carcinogenic risks posed by contaminants were estimated by computing the HHI for each
chemical in accordance with procedures established by EPA. An HHI greater than 1.0 indicates a
potential health threat. The noncarcinogenic risks posed by arsenic and cadmium are shown on
Table 5. The aggregate estimated HHIs from arsenic and cadmium due to the combined effects of
all pathways are:
• 5.8 for Future Oxidation Lagoons Residents;
• 2.1 for Future Drainage Ditches and Old Morrison Creek Residents;
• Less than 1.0 for the Nearest Off-site Business and Nearest Off-site Resident.
For lead, which may cause decreased neurological development in children, the U.S. EPA has
developed a biokinetic model for evaluating lead exposures on a site-specific basis. Using the
model, potential blood lead levels in children can be calculated and then evaluated by comparing
them to the level which the U.S. EPA estimates will cause adverse effects in children [10
micrograms per deciliter (ug/dl)] (U.S. EPA, 1990c).
Based upon a calculated upper-bound surface soil lead concentration of 194 milligrams per
kilogram (egual to the 95 percent upper confidence limit of the mean), the geometric mean blood
level in children (0 to 6 years old) that reside at the Oxidation Lagoons would be 4.88 ug/dl
due to soil ingestion. Additionally, the blood lead level in 98.12 percent of the population
would be less than the suggested U.S. EPA criterion of 10 ug/dl. These results indicate that
lead in surface soils at the Oxidation Lagoons Operable Unit is a low concern with respect to
human health.
Therefore, the baseline risk assessment indicates a potential noncarcinogenic health threat to
Hypothetical Future On-Site Residents due to the metals at the site, but no non-carcinogenic
health threat to the Nearest Off-Site Business or Residents.
Health risk assessment provides a means of guantifying potential risks posed by chemicals
present in the environment. However, a great deal of uncertainty exists in the estimation
process. In addition to uncertainties common to the risk assessment process, sources of
uncertainty in the PHE conducted for the Oxidation Lagoons Operable Unit include:
Site Characterization -- Chemicals may exist in localized "hotspots" where samples were not
collected, or chemicals may exist at the site but may not have been detected by the selected
analytical methods. This could result in an underestimation of risk.
Estimation of Exposure Point Concentrations — These may be overestimated since (1) chemicals
reported as "non-detects" are assigned a value of one-half the detection limit for the purpose
of calculating site concentrations, and (2) the PHE assumes that chemical concentrations in soil
and groundwater remain constant over the 70-year exposure period, rather than decreasing as
expected due to leaching. This could result in overestimating the risk.
Actual or threatened releases of hazardous substances from this site, if not addressed by
implementing the response action selected in this ROD, may present an imminent and substantial
endangerment to public health, welfare, or the environment.
6.2 Environmental Evaluation
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The SAAD site is primarily a disturbed annual grassland ecosystem. No threatened plant or animal
species inhabit the site. Several sensitive species have been observed, including the burrowing
owl, black-shouldered kite, and American kestrel.
Remediation activities at the Oxidation Lagoon Operable Unit will disrupt the existing habitat,
including riparian vegetation present on the perimeters of the lagoons. The riparian habitat
developed as a result of the wastewater formerly stored in the lagoons. In the opinion of a
retired California Fish and Game representative who investigated the site, the lagoons are only
a passage way for animals, except for ground sguirrels. Ingestion of the sguirrels by foxes and
great horned owls could result in their exposure to heavy metals. This could result in death and
deformity of young, and health problems for adults. Remediation, therefore, would favor wildlife
and appears to warrant disruption of the existing habitat.
A study of plants and soils was conducted at the Sacramento Army Depot on September 6, 1991.
The objective of the study was to evaluate historically wet areas to determine if they fit the
criteria for jurisdictional wetlands, as regulated by Section 404 of the Clean Water Act. The
assessment was based on the Corps of Engineers' criteria for wetland delineation: hydric soils,
hydrophytic vegetation, and wetland hydrology.
The wetlands delineation indicated that Old Morrison Creek and a small bathtub-like feature
north of the Oxidation Lagoons display the hydric soils, hydrophytic plants, and hydrology
needed to gualify as jurisdictional wetlands. The total area of jurisdictional wetlands amounts
to approximately 0.52 acre. These seasonal wetlands are isolated from other waterbodies. The
Corps of Engineers has concluded that these wetlands are not high guality and provide minimal
wetland functions and habitat value. In addition, field surveys conducted at the time of this
study and on two other occasions, November/December 1991 and April/May 1992, indicated there are
no threatened or endangered species inhabiting the area.
The following reguirements are ARARs for all alternatives:
Section 404 of the Clean Water Act, 33 U.S.C. Section 1344, reguires permits for the discharge
of dredged or fill material into waters of the United States, including wetlands. The 404(b)
(1) regulations (40 CFR Part 230) and Executive Order 11990, "Protection of Wetlands", dated May
24, 1977, reguire Federal agencies to avoid adversely impacting wetlands wherever possible, and
to preserve the functional values of wetlands. The nationwide permits (NWP) program, set forth
in 33 CFR Part 330 and administered by the Army Corps of Engineers, is designed to regulate with
little, if any, delay or paperwork certain activities having minimal impacts. The types of NWPs
and conditions under which a permit is granted are given in Appendix A to Part 330.
Because the wetlands at SAAD exhibit low wetland functional values, the Army Corps of Engineers
has determined that the proposed fill activities-- replacement of excavated soil into the
wetlands area of the Oxidation Lagoons-would result in minimal adverse impacts and is work of a
nature specifically authorized under both NWPs 26 and 38. Although CERCLA Sec. 121 (e) provides
that permits are not reguired for activities conducted entirely on-site, the Army Corps of
Engineers has determined that the replacement of the excavated soil is properly authorized under
the terms of NWP 26, "Headwaters and Isolated Waters Discharges". The wetland area proposed to
be impacted at SAAD gualifies as an "isolated water", defined as non-tidal waters of the United
States that are: (1) Not part of a surface tributary system to interstate or navigable waters
of the United States; and (2) Not adjacent to such tributary waterbodies. Following remediation,
the Army plans to restore the impacted wetland area by regrading and revegetating, as described
in Section 1.10.
6.3 Cleanup Levels
Based upon the results of the PHE, cleanup levels were established for the three primary metals
of concern: arsenic, cadmium, and lead.
Arsenic and cadmium are the primary metals of concern due to potential carcinogenic effects.
Arsenic poses a risk as a potential carcinogen via soil ingestion, dermal absorption, and
groundwater ingestion. Cadmium poses a risk as a potential carcinogen via dust inhalation.
Cadmium also poses a risk for noncarcinogenic effects via dermal absorption and groundwater
ingestion. Specific risk numbers were not developed in the PHE for lead. However, lead is a
metal of concern primarily because it poses risks as a reproductive toxin and can effect the
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central nervous system in children.
One other metal assessed in the PHE, antimony poses a risk for noncarcinogenic effects via
groundwater ingestion. Antimony was only detected in 3 of 62 samples analyzed. Therefore, it
does not appear to exist throughout the site. However, the health risk assessment assumed that
antimony is present throughout the site at an upper-bound concentration of 28 mg/kg. This
concentration is less than the Federally proposed action level of 30 mg/kg. Exceeding the
proposed action level could indicate that further assessment is warranted. Since this proposed
action level is not exceeded and since antimony was detected in less than 5 percent of samples
analyzed, a specific cleanup level was not established. Some cleanup of antimony will be
achieved in the process of cleaning up other metals of concern.
Specific soil cleanup levels for other metals found above background levels were not developed.
Based upon results of the PHE, the concentrations of these metals in soil do not pose
unacceptable health risks.
The selected cleanup levels will reduce contaminant levels in soil. A list of Comparative
Criteria is provided on Table A-l, Appendix A. The cleanup levels are shown in Table 6, and are
discussed below.
6.3.1 Non-Carcinogens
Of the three primary metals of concern, only cadmium exceeds the acceptable HHI of 1.0. A
cleanup level was developed for cadmium. Additionally, a cleanup level was established for lead
for the reasons described above. The cleanup levels will result in reductions of risk by 91
percent for cadmium, and by 10 percent for lead.
6.3.2 Carcinogens
Of the three primary metals of concern, arsenic and cadmium are carcinogens. The proposed soil
cleanup level for arsenic would result in a risk reduction of 50 percent. As stated above, the
proposed cleanup level for cadmium would result in a 91 percent risk reduction.
7 DESCRIPTION OF ALTERNATIVES
An OUFS was conducted to develop and evaluate remedial alternatives for the Oxidation Lagoons
Operable Unit. Fourteen remedial alternatives were assembled from applicable remedial
technology process options, and were initially evaluated for effectiveness, institutional
implementability, and cost. Five alternatives for cleaning up soil at the Oxidation Lagoons
passed this initial screening and were then considered in detail by comparing them to the nine
criteria reguired by the NCP. The remedial alternatives emphasize the use of technologies which
reduce toxicity, mobility, or volume of contaminants, and which provide a permanent solution.
In addition to the remedial alternatives, the NCP and CERCLA reguire that a no-action
alternative be considered at every site. The no-action alternative serves primarily as a
point-of-comparison for other alternatives. The five alternatives evaluated are:
• Alternative 1: No Action
• Alternative 2: Excavation, On-Site Soil Washing, On-Site Treatment of Wash Liguid,
and Backfill with Washed Soil
• Alternative 3: Excavation, On-Site Soil Washing, Off-Site Disposal of Wash Liguid,
and Backfill with Washed Soil
• Alternative 4: Excavation, Stabilization, and Backfill with Stabilized Soil
• Alternative 5: Excavation, Stabilization, Backfill with Stabilized Soil, and Cap
Each alternative would be applied to remediate approximately 15,500 cy of soil that contain the
contaminants detected at the site at concentrations exceeding cleanup levels. The location and
configuration of the 15,500 cy are shown in Figures 3 and 4. Each alternative is expected to
attain the treatment levels (cleanup levels) described in Section 6.3. Each alternative can be
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implemented, subject to the difficulties and considerations described in Section 8.6. During
implementation of each alternative, controls will be exercised to reduce the disruption to
wildlife in the area, including removal of trees prior to nesting season to encourage nesting
activity in alternative locations. The five alternatives are described in more detail in the
following sections.
7.1 Alternative 1: No Action
Under this alternative, the Army would take no further action to control the source of
contamination. However, long-term monitoring of the site would be necessary to monitor
contaminant migration. Since periodic groundwater monitoring is presently being conducted, it
is assumed that the current monitoring program would be continued under this alternative.
Because this alternative would result in contaminants remaining on site, CERCLA reguires that
the site be reviewed every five years. If indicated by the review, remedial actions would be
implemented at that time to remove or treat the wastes.
Based upon the health risk assessment, cadmium and arsenic left on site in present
concentrations pose potential threats to public health and the environment. Specifically, the
human health risks estimated for hypothetical future residents exceed levels normally considered
acceptable. Additionally, ingestion of sguirrels by foxes and great-horned owls could result in
ecological exposure to heavy metals. The "No Action" alternative therefore does not meet the
threshold criteria of protectiveness of human health and the environment. Alternatives which do
not meet this first evaluation criterion are not acceptable remediation alternatives and further
evaluation is not necessary.
7.2 Alternative 2: Excavation, On-site Soil Washing, On-site Treatment of Wash Liquid, and
Backfill with Washed Soil
Alternative 2 consists of excavating contaminated soil and treating it in an on-site washing
unit. Soil samples would be collected from the excavation to assess whether contaminated soil
remains. Dust created while excavating would be controlled using water or foam sprays.
The washing unit would consist of a size segregation device, mix reactors, and a de-watering
device. Oversized soil particles would be segregated using wet screens to physically remove
contaminants from the larger size fraction. The segregated lower size fraction would be
transferred to mix reactors, where it would be mixed with a washing reagent. Based upon
treatability testing results, a combination of chelating agents and dilute acid solution with a
minimum reaction time of 30 minutes would probably be used to meet the cleanup levels.
After the soil and washing reagent are mixed for a selected reaction time, the soil/reagent
slurry would be de-watered. De-watering would be accomplished using a centrifuge or
vacuum/pressure filters. The washed soil fraction would be recovered, and the rinsate would be
stored in holding tanks for recycling. Composite samples would be collected from the washed soil
to evaluate the effectiveness of the cleanup. Remediated soil would be replaced in the
excavation.
The soil wash rinsate would be treated on site using a chemical precipitant. Dissolved metals
would be converted to insoluble forms, and would be separated from the rinsate using a
clarifier. Flocculation and settling of the metals may be further enhanced by the addition of
chemical coagulants. The sludge containing precipitated metals would be de-watered on site and
disposed at an off-site facility permitted to receive hazardous waste. Stabilization of the
de-watered sludge may be reguired to minimize its leaching potential.
As an alternative, the precipitated metals could be recovered at an off-site metal reclamation
unit. The decision to use reclamation will depend upon the concentration of metals in the
sludge, the total amount of sludge, the cost, and the availability of a market for metals
recycling.
Samples of the treated rinsate would be analyzed to assess its guality. Treated rinsate would be
discharged to the sanitary sewer after demonstrating compliance with SAAD's sewer use permit
conditions.
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Alternative 2 would be protective of human health and the environment. The protection is
achieved by removing metals from the soil. The heavy metals were estimated in the public health
evaluation to present an unacceptable risk to a hypothetical future resident and were found in
the environmental evaluation to be a potential risk to predators.
Soils would be excavated and then treated until sampling and analysis indicates that the
remaining unexcavated soil as well as the treated soil contain heavy metals at either the local
background levels or at the prescribed clean-up level. Clean-up levels, as presented in Section
6.3, are soil concentrations developed for three of the heavy metals which must be met in order
for the soil not to pose unacceptable risks to human health or the environment.
Alternative 2 will be conducted in full compliance with ARARs, as listed on Table A-2. U.S. EPA
has approved the State of California's application for RCRA authorization, effective August 1,
1992. Therefore, all Federal RCRA regulations (40 CFR Parts 262 through 268) cited as ARARs in
Table A-2 are now superceded by the corresponding State RCRA regulations. The site-specific
ARARs are California Health and Safety Code Sections 25208.1 and 25208.4 and Sections 2580, 2582
and 2524 of Chapter 15, Title 23, California Code of Regulations (CCR). These ARARs address
closure reguirements for surface impoundments. The Health and Safety Codes (also known as the
Toxic Pits Cleanup Act or TPCA) will be met by achieving closure of these surface impoundments.
The sections of 23 CCR will be met by removing the old surface impoundment structures and
contaminated geologic material. The term "contaminated" used in the regulation has been defined
for this project by the development of cleanup levels. Also, because the SESOIL Modeling
demonstrates that the proposed soil cleanup and residual levels will not impact ground or
surface waters, these soils can be classified as 'Inert Waste' per California's Title 23 Chapter
15, Section 2524, CCR. However, to confirm that the actual remediated and residual soils meet
the 'Inert Waste' classification, they will be sampled and analyzed (using the deionized water
Waste Extraction Test) to verify the SESOIL Modeling results.
State Water Resources Control Board Resolution 68-16 (the Anti-Degradation Policy) has been
incorporated into the Water Quality Control Plan for the Central Valley Regional Water Quality
Control Board (Basin Plan). The CVRWQCB has identified this as an ARAR for all remedial
alternatives. Compliance with this ARAR reguires that the guality of the underlying groundwater
must be maintained following the implementation of the soil remedy. Compliance with the soil
cleanup levels set forth in Table 6 of this ROD, and with the closure and sampling and analysis
reguirements specified in the preceding paragraph, will constitute compliance with Resolution
68-16.
A number of action and chemical specific ARARs have been identified for this alternative. The
action specific ARARs will be achieved by the remediation contractor taking the necessary
actions to comply. Chemical specific ARARs will be met by designing the remediation system for
achieving the desired result and monitoring for compliance.
The soils at the Oxidation Lagoons contain both RCRA listed F006 waste and characteristic
hazardous waste (arsenic and mercury which exceed their toxic characteristic values).
Replacement of the excavated soil after treatment would reguire compliance with RCRA ARARs for
disposal of hazardous waste, including the land disposal restrictions. The RCRA Land Disposal
Restrictions (LDRs) are ARARs for all remedial alternatives.
Alternative 2 would comply with LDRs through either the treatment standards in 40 CFR 268.41
(now 22 CCR 66268.41) or a treatability variance under 40 CFR 268.44 (now 22 CCR 66268.44).
Existing treatability study data do not conclusively demonstrate that the LDR treatment
standards can be attained. Thus, prior to full scale implementation of the soil washing remedy,
a pilot test will be conducted. If the pilot test shows that the treatment standards (268.41)
are not achievable, the alternative treatment levels shall apply through a treatability variance
under 268.44.
In complying with LDRs, the following items are "to be considered":
EPA's Superfund LDR Guide #6A, Superfund Publication 9347.3-06FS
OSWER Memo, Lowrance to Luftig, April 6, 1990.
As set forth in the Lowrance memo, Minimum Technology Reguirements (MTRs) for land disposal of
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RCRA restricted waste would not be triggered by placing the treated soil back into the excavated
Oxidation Lagoons area as long as there is no lateral expansion of the original areas of
contamination.
7.3 Alternative 3: Excavation, On-Site Soil Washing, Off-Site Disposal of Wash Liquid, and
Backfill
Alternative 3 consists of excavating contaminated soil and treating it in an on-site washing
unit. Alternative 3 is identical to Alternative 2, except that the rinsate generated during
soil washing operations would be treated off site.
Compliance with ARARs would be the same as described for Alternative 2 and as stated in Table
A-2, except that the wash water will be disposed off site. As noted on Table A-2, 40 CFR 403 is
applicable for Alternative No. 2 only since Alternative No. 3 would not use disposal to the
regional POTW. Otherwise, Table A-2 applies to both alternatives.
The wash water would be subject to the same regulations as the heavy-metal containing sludge
which is produced for offsite diposal or recycling. The wash water will be analyzed to
determine the appropriate disposal methods and reguirements.
7.4 Alternative 4: Excavation, Stabilization, and Backfill with Stabilized Soil
Alternative 4 consists of excavating and stabilizing contaminated soil. Stabilization would be
accomplished using pozzolanic-based additives, such as Portland cement. Pre-determined
guantities of cement, silicates, and water would be mixed and added to the soil. The mixture
would be homogenized in mix drums and allowed to cure. Alternative mixing and curing
procedures, including in-situ procedures, are feasible.
Stabilization depends on developing a suitable "mix design" or recipe for soil, cement, and
other additives. With a proper recipe, the heavy metals are immobilized in the soil mass to
meet leachability criteria. The leachability criteria, as measured by the Toxic Characteristic
Leaching Procedure (TCLP), is established at levels which are protective of human health and the
environment.
Compressive strength and permeability criteria are added to the engineering design to improve
the permanence of the remediation and reduce maintenance reguirements. The soil mass, after
mixing in the additives, would be returned to the oxidation lagoons and backfilled in place.
Verification testing would be used to ensure leachability and other criteria are being met at
all times.
The site-specific ARARs for Alternative 4 are the same as for other alternatives. Compliance is
also the same in that this remediation will close the surface impoundments. Closure will be
achieved via excavation and removal of surface impoundment structures and contaminated geologic
materials. The cleanup levels would guide excavation and the remaining, unexcavated soil would
not pose significant human health or environmental risks.
Stabilized soil would meet the criteria of an inert waste. Stabilized soil would not be
significantly leachable or pose other human health or environmental risks.
Action-specific and chemical specific ARARs will be achieved by design and contractor adherence
to the ARARs. Placement of the stabilized soil back into the oxidation lagoons will not expand
the area of contamination; therefore, minimum technology reguirements for a landfill are not
applicable.
One reguirement was found to be relevant and appropriate. Future site owners and operators
shall be notified of the existence of the stabilized soil mass. The Army shall develop a
notification procedure.
Table A-3 provides a list of ARARs for Alternative No. 4.
7.5 Alternative 5: Excavation, Stabilization, Backfill with Stabilized Soil, and Cap
Alternative 5 consists of excavating and stabilizing contaminated soil. Alternative 5 is
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identical to Alternative 4, except that the stabilized soil would be capped after it is returned
to the site. Alternative 5 would be selected if stabilized soil does not comply with
leachability criteria set for cadmium.
The cap would be approximately 5 feet thick, and would consist of vegetative and drainage layers
overlying a 40 millimeter-thick plastic liner and a clay layer. The cap would be sloped at
approximately 3 percent.
Alternative 5 would comply with the same ARARs as Alternative No. 4 in the same manner as
described above. The higher leachability of cadmium is not expected to pose a significant human
health or environmental risk. However, additional State of California regulations would be
applicable. These are 22 CCR 66264.301 (d) and (g) and 22 CCR 264.303 and 22 CCR 264.310. The
feasibility study analysis provides sufficient demonstration that a liner is not reguired for
placement of the stabilized soil back into the oxidation lagoons.
8 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
The five remedial alternatives have been assessed using the nine evaluation criteria developed
to address CERCLA reguirements. The nine criteria are:
Threshold Criteria
1) Overall Protection of Human Health and the Environment
2) Compliance with Applicable or Relevant and Appropriate Reguirements (ARARs)
Primary Balancing Criteria
3) Long-Term Effectiveness and Permanence
4) Reduction of Toxicity, Mobility, or Volume (TMV)
5) Short-Term Effectiveness
6) Implementability
7) Cost
Modifying Criteria
8) State Acceptance
9) Community Acceptance
The following sections compare the five remedial alternatives in terms of each of the nine
criteria.
8.1 Overall Protection of Human Health and the Environment
This criterion assesses whether the alternative meets the statutory reguirement for protection
of public health and the environment, and describes how risks posed through each potential
exposure pathway are eliminated, reduced, or controlled through treatment, or engineering or
institutional controls. This criterion is based upon the findings of three other evaluation
criteria: "Compliance with ARARs", "Long-Term Effectiveness and Permanence", and "Short-Term
Effectiveness".
Each of the alternatives, except Alternative 1 (no action), would provide adeguate protection of
human health and the environment. Potential risks due to groundwater ingestion and inhalation
of dust would be reduced to levels that are acceptable to the U.S. EPA and the DTSC.
Alternatives 2 through 5 would reduce risks by excavating contaminated soil. Alternatives 2 and
3 treat the soil to an inert waste by washing out the contaminants. Alternative 4 treats the
soil to an inert waste by stabilization. Alternative 5 includes stabilization of soil to levels
that are protective of human health and the environment.
Risks temporarily posed due to the potential of increased dust inhalation exposure would be
reduced by controlling dust with water or foam sprays. Risks temporarily posed to workers due to
dermal exposure during excavation activities would be reduced by the use of protective clothing.
Additionally, workers would follow OSHA guidelines for working on an hazardous waste site and
ambient air guality would be monitored continuously.
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8.2 Compliance with ARARs
Compliance with ARARs was not evaluated for Alternative No. 1 since this alternative did not
meet the threshold requirement of protectiveness. Alternatives 2 through 5 were each found to
comply with ARARs. Compliance is achieved as discussed in Section 7 of this document. A
treatability variance from land disposal restrictions is likely to be required for alternatives
2 through 5. The achievable treatment levels will be set by field pilot tests employing the
selected technology.
8.3 Long-Term Effectiveness and Permanence
The analysis of long-term effectiveness and permanence addresses the expected residual risk, and
the ability of a remedy to maintain reliable protection of human health and the environment
after the remedial objectives have been attained.
Alternatives 2, 3, 4, and 5 include excavation of the chemicals of concern present at
concentrations exceeding cleanup levels. Alternatives 2 and 3 include treating soil to
acceptable risk levels. Alternatives 4 and 5 include stabilization of the soil to reduce
contaminant mobility. Each of these alternatives affords long-term effectiveness and
permanence. Alternatives 2 and 3 are more permanent than Alternatives 4 and 5, since the
contaminants would be removed from the site.
8.4 Reduction of Toxicity, Mobility, or Volume through Treatment
The analysis of this criterion addresses the anticipated performance of the treatment
technologies the remedy may employ. The analysis considers:
• treatment process;
• volume of hazardous material to be treated;
• effectiveness in reducing toxicity, mobility, and volume of contaminant; and;
• type of quantity of treatment residual.
Alternatives 2 and 3 would remove the contaminants from the site, which would effectively
reduce on-site mobility, toxicity, and volume. Alternatives 4 and 5 would decrease contaminant
mobility, which would result in a reduction in toxicity. However, Alternatives 4 and 5 would
also increase the volume of contaminated material on site due to the addition of cement or other
stabilizers.
8.5 Short-Term Effectiveness
The analysis of short-term effectiveness addresses public health and environmental impacts
during the construction and implementation period. The period of time required to achieve
remediation objectives is also considered. The time required to complete the five alternatives
are as follows:
• Alternative 1 - None
• Alternative 2 - 6 to 9 months
• Alternative 3 - 6 to 9 months
• Alternative 4-3 months
• Alternative 5 - 3 to 6 months
Alternative 1 is effective in the short term. The Oxidation Lagoons are secure, eliminating the
possibility of soil ingestion. The majority of the site is overgrown with vegetation, limiting
dust formation. Based upon absence of evidence of contaminant metals in soil below 3 feet or in
groundwater, downward migration of metals does not appear to be occurring.
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Alternatives 2, 3, 4, and 5 would slightly increase the potential for dust exposure during
construction activities. This could result in a short-term increase in human health risks. The
exposures would be controlled to acceptable levels and monitored.
8.6 Implementability
Implementability refers to the technical and administrative feasibility of performing the
remedial alternative. The analysis also considers the availability of necessary materials and
services. The following factors were considered:
• Ability to construct the technology;
• Reliability of the technology;
• Ease of interfacing additional remedial technology;
• Feasibility of monitoring;
• Ability to obtain approvals from, and coordinate with, regulatory agencies;
• Availability of treatment, storage, and disposal services; equipment and
specialists; and technologies.
Alternative 1 could be readily implemented. Alternative 4 could be readily implemented, subject
to preparation of a suitable mix design. Based upon results of the mix design treatability
studies, modifications would be required to develop a mix which would stabilize the soil
sufficiently to comply with ARARs. If an adequate mix design cannot be developed, Alternative 5
could readily be implemented, subject to approval of the cap design. Alternatives 2 and 3 rely
on a process which has been proven in the laboratory and is believed to be feasible. A pilot
study will be conducted at the site to demonstrate the feasibility of the process prior to full-
scale implementation.
8.7 Cost
This criterion evaluates the capital and operation and maintenance (O&M) costs, and present
worth of each alternative. The estimated costs as of August 1991 for each alternative were as
follows:
Present Capital O&M
Alternative Worth Cost Cost
Alternative 1 $0 $0 $0
Alternative 2 $5,020,000.00 $5,020,000.00 $0
Alternative 3 $4,556,000.00 $4,556,000.00 $0
Alternative 4 $2,574,000.00 $2,574,000.00 $0
Alternative 5 $3,800,000.00 $3,800,000.00 $0
Since all of the alternatives require less than one year to complete, the estimated costs are
capital costs. No recurring O&M costs are expected. These costs are estimates and actual
contractor bids may differ from the estimates. The contractor's bid for Alternative 2, the
selected remedy, is $8.9 million. The difference in cost is associated with more detailed
information presented by the contractor. The Army analyzed the contractor's cost estimate and
determined that it was fair and reasonable. It is anticipated that the contractor cost estimate
for the other alternatives would be similarly higher.
Alternative 1 is the least expensive. Alternatives 4 and 5 would cost 25 to 50 percent less
than Alternatives 2 and 3.
8.8 State Acceptance
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The analysis of State acceptance addresses technical and administrative concerns of the U.S.
EPA, the DTSC, the SMAQMD, and the RWQCB relative to implementation of the remedial alternative.
The State of California has concurred with the selected alternative for the cleanup of soil at
the Oxidation Lagoons. The State of California Department of Toxic Substances Control has
adopted a Negative Declaration, pursuant to the California Environmental Quality Act (CEQA) .
8. 9 Community Acceptance
This criterion indicates whether the public concurs with, opposes, or has no comment on the
preferred alternative. During the public meeting and two public comment periods, the public
reguested information on the results of the treatability testing, the use of Superfund money,
the effects of the cleanup on Depot wildlife, the applicability of bioremediation, the effects
of rainfall, and the feasibility of achieving a lower cleanup level for lead in soil. The
public did not indicate concerns about the preferred alternative. Part III of this ROD contains
the Responsiveness Summary from the public comment periods and public meeting.
9 SEIiECTED REMEDY
Alternative 2 is the remedy selected for the cleanup on the soil at the Oxidation Lagoons
Operative Unit. The selection of this remedy was based upon the comparative analysis of
alternatives presented above, and provides the best balance of trade-offs with respect to the
nine evaluation criteria. The selected remedy consists of the following components:
• excavating contaminated soil;
• washing contaminated soil on-site to remove chemicals of concern;
• replacing washed soil into the excavation;
• treating soil-washing rinsate on-site;
• disposing treated rinsate in the sanitary sewer;
• treating and disposing of the de-watered residual sludge off-site; consisting of
stabilization and disposal in a RCRA landfill, or recovery of metals at an off-site
reclamation unit.
No air emissions are anticipated; dust would be controlled during excavation using water or foam
sprays.
The objective of the remedial action is to reduce the toxicity, mobility, and volume of
contaminants at the Oxidation Lagoons Operable Unit such that:
• remaining contaminant concentrations are in compliance with ARARs; and
• human health and the environment are protected.
The selected remedy would cost more than the other alternatives which were considered; however,
it would meet the objectives of the remedial action most effectively. The total estimated cost
for the selected remedy is $5,020,000.00. The itemized cost estimate is presented on Table 7.
Because the remedy is expected to take six to nine months, recurring operation and maintenance
costs are not expected. Therefore, Capital Cost eguals the Present Worth of the alternative.
The selected remedy would provide short-term effectiveness, and is technically feasible. It
would provide better short-term effectiveness than Alternative 3, because the latter would
involve transporting hazardous rinsate off-site for treatment; this could temporarily increase
human health and environmental risks.
The selected remedy would provide long-term effectiveness by maintaining protection of human
health and the environment. The selected remedy would be more permanent than Alternatives 4 and
5, because the contaminants would be removed from the site.
The selected remedy would reduce toxicity, mobility, and volume of the contaminant through
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treatment more effectively than Alternatives 4 and 5. The latter two alternatives would increase
the volume of contaminated material due to the addition of a soil stabilizer.
The selected remedy is expected to comply with ARARs. A treatability variance may be required
in order to meet the Landban TCLP criterion. The ARARs for the selected remedy are discussed in
Table A-2.
10 STATUTORY DETERMINATIONS
The Army's primary responsibility at this NPL site is to undertake remedial actions that achieve
adequate protection of human health and the environment. Section 121 of CERCLA establishes
several statutory requirements and preferences. These specify that, when complete, the selected
remedy must comply with ARARs unless a statutory waiver is justified. The selected remedy must
also be cost effective, and utilize permanent solutions and alternative treatment or resource
recovery technoloqies to the maximum extent practicable. Finally, the statute expresses a
preference for remedies that reduce toxicity, mobility, or volume of the hazardous waste.
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ALTERNATIVE 2 NOTES:
1 Includes workplan preparation, sampling and analysis, soil washing tests, and report
2 Includes trees and concrete valve boxes
3 Assumes electrical connection reguires a transformer and the water connection a tap to ground
water treatment plant
4 Based on fence surrounding oxidation lagoons and staging area
Site improvements includes a barrier along north side of oxidation lagoons for laser protection
5 Includes hydroseeding oxidation lagoons
6 Includes site restoration, water treated on-site and disposed of in sanitary sewer
7 Based on removing and replacing 15,500 in-place c.y. soil
8 Based on 66 surface samples analyzed for EPA 6010, Cd and Pb atomic adsorption, QA/QC,
report, 100% rush
9 Based on excavation verification survey
10 Soil washing system includes treatment sampling verification and wash liguid treatment Based
on 15,500 in-place c.y. soil @ $155/c.y.
11 Based on 66 3'-5' borings analyzed for EPA 6010, Cd and Pb atomic adsorption, QA/QC, report,
100% rush
12 Based on 5% of construction costs excluding reports
13 Based on anticipated reports
14 Based on percentage of the construction costs
15 Based on 1991 dollars
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10.1 Protection of Human Health and Environment
The selected remedy would protect human health and the environment by removing the contaminated
material from the site. Risks posed by ingestion of contaminated soil and groundwater would be
eliminated. Risks posed by fugitive dust inhalation could be temporarily increased during
construction, but would be eliminated once the remediation is accomplished. To reduce inhalation
risks during construction, dust would be controlled with water or foam sprays.
Because this remedy will not result in hazardous substances on site above health-based levels
(providing the variance for cadmium is granted; see Section 10.2 below), the 5-year review will
not apply to this action.
10.2 Compliance with ARARs
The selected alternative complies with ARARs as listed in Table A2 . Detailed design and pilot
testing of the soil washing process has not yet been completed. When completed, the design data
will determine the exact method of compliance with certain regulations.
10.3 Cost Effectiveness
The selected remedy is cost-effective in mitigating the principle risks within a reasonable
period of time. The estimated cost of the selected alternative is $5,020,000, which is slightly
higher than the cost for Alternative 3 and about 25 to 50 percent higher than estimated costs
for Alternatives 4 and5. The no-action alternative is not acceptable since it does not protect
human health and the environment. Additionally, the selected remedy would be more effective in
protecting human health and the environment, and would be more permanent than Alternatives 3, 4,
and 5. Therefore, the estimated cost for the selected remedy is reasonable considering these
criteria.
10.4 Utilization of Permanent Solutions and Alternative Treatment Resource Recovery
Technologies
The selected remedy represents the maximum extent to which permanent solutions and treatment
technologies can be used in a cost-effective manner at the Oxidation Lagoons Operable Unit. Of
those alternatives that are protective of human health and the environment, and comply with
ARARs, the selected remedy provides the best balance of tradeoffs in terms of:
• Reduction of toxicity, mobility, and volume of contaminant through treatment:
Treatment would consist of washing soil, and adding precipitants to rinsate to
remove metals. Treatment of the soil and rinsate would reduce or eliminate the risk
to human health and the environment posed by the contaminants of concern.
• Long-term effectiveness and permanence: Metals, in residual sludge, would be
removed from the site, resulting in a permanent remedial solution. Resource
recovery technologies would be utilized, if economically practicable, to salvage
metals from the residual sludge.
10.5 Preference for Treatment as a Principle Element
The selected remedy satisfies the statutory preference for treatment as a principle element.
The principle threat to human health and the environment is heavy metal contamination in soil.
The selected remedy will reduce heavy metals concentrations through treatment, consisting of
soil washing. Heavy metals will be removed from soil-wash rinsate through treatment, consisting
of the addition of precipitants.
11 DOCUMENTATION OF SIGNIFICANT CHANGES
There were no significant changes from the Proposed Plan issued in April 1992.
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12 REFERENCES CITED
California Air Pollution Control Officers Association (CAPCOA) , 1987, Toxics Air Pollutant
Source Assessment Manual for California Air Pollution Control Districts and Applicants for Air
Pollution Control District Permits; Interagency Working Group, CAPCOA, Cameron Park, California.
United States Environmental Protection Agency, 1986, Superfund Public Health Evaluation Manual,
EPA 540/1-86/060; U.S. Environmental Protection Agency, Office of Emergency and Remedial
Response, Washington, D.C.
, 1989, Risk Assessment Guidance for Superfund, Human Health
Risk Assessment, U.S. EPA Recommendations; U.S. Environmental Protection Agency, Region IX, San
Francisco, California.
f iggoa, Integrated Risk Information System (IRIS); U.S.
Environmental Protection Agency, Washington, D.C.
, 1990b, Health Effects Assessment Summary Tables, Third
Quarter FY 1990; U.S. Environmental Protection Agency, Office of Solid Waste and Emergency
Response, Washington, D.C.
, 1990c, User's Guide for Lead: a PC Software Application of
the Uptake/Biokinetic Model, Version 0.40; U.S. Environmental Protection Agency, Environmental
Criteria and Assessment Office, Cincinnati, Ohio.
, 1990d, Policy Memorandum: "CERCLA Response Activities and
the Land Disposal Restrictions Program's Applicability at Plattsburgh Air Force Base;" From
Sylvia Lowrance, Director of Office of Solid Waste, April 6, 1990.
APPENDIX A
ANALYSIS OF ARARs
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